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perf: Add build id data in mmap2 event
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Adding support to carry build id data in mmap2 event.

The build id data replaces maj/min/ino/ino_generation
fields, which are also used to identify map's binary,
so it's ok to replace them with build id data:

  union {
          struct {
                  u32       maj;
                  u32       min;
                  u64       ino;
                  u64       ino_generation;
          };
          struct {
                  u8        build_id_size;
                  u8        __reserved_1;
                  u16       __reserved_2;
                  u8        build_id[20];
          };
  };

Replaced maj/min/ino/ino_generation fields give us size
of 24 bytes. We use 20 bytes for build id data, 1 byte
for size and rest is unused.

There's new misc bit for mmap2 to signal there's build
id data in it:

  #define PERF_RECORD_MISC_MMAP_BUILD_ID   (1 << 14)

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/bpf/20210114134044.1418404-4-jolsa@kernel.org
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Jiri Olsa authored and Alexei Starovoitov committed Jan 15, 2021
1 parent 921f88f commit 88a16a1
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Showing 2 changed files with 65 additions and 9 deletions.
42 changes: 37 additions & 5 deletions include/uapi/linux/perf_event.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -386,7 +386,8 @@ struct perf_event_attr {
aux_output : 1, /* generate AUX records instead of events */
cgroup : 1, /* include cgroup events */
text_poke : 1, /* include text poke events */
__reserved_1 : 30;
build_id : 1, /* use build id in mmap2 events */
__reserved_1 : 29;

union {
__u32 wakeup_events; /* wakeup every n events */
Expand Down Expand Up @@ -659,6 +660,22 @@ struct perf_event_mmap_page {
__u64 aux_size;
};

/*
* The current state of perf_event_header::misc bits usage:
* ('|' used bit, '-' unused bit)
*
* 012 CDEF
* |||---------||||
*
* Where:
* 0-2 CPUMODE_MASK
*
* C PROC_MAP_PARSE_TIMEOUT
* D MMAP_DATA / COMM_EXEC / FORK_EXEC / SWITCH_OUT
* E MMAP_BUILD_ID / EXACT_IP / SCHED_OUT_PREEMPT
* F (reserved)
*/

#define PERF_RECORD_MISC_CPUMODE_MASK (7 << 0)
#define PERF_RECORD_MISC_CPUMODE_UNKNOWN (0 << 0)
#define PERF_RECORD_MISC_KERNEL (1 << 0)
Expand Down Expand Up @@ -690,6 +707,7 @@ struct perf_event_mmap_page {
*
* PERF_RECORD_MISC_EXACT_IP - PERF_RECORD_SAMPLE of precise events
* PERF_RECORD_MISC_SWITCH_OUT_PREEMPT - PERF_RECORD_SWITCH* events
* PERF_RECORD_MISC_MMAP_BUILD_ID - PERF_RECORD_MMAP2 event
*
*
* PERF_RECORD_MISC_EXACT_IP:
Expand All @@ -699,9 +717,13 @@ struct perf_event_mmap_page {
*
* PERF_RECORD_MISC_SWITCH_OUT_PREEMPT:
* Indicates that thread was preempted in TASK_RUNNING state.
*
* PERF_RECORD_MISC_MMAP_BUILD_ID:
* Indicates that mmap2 event carries build id data.
*/
#define PERF_RECORD_MISC_EXACT_IP (1 << 14)
#define PERF_RECORD_MISC_SWITCH_OUT_PREEMPT (1 << 14)
#define PERF_RECORD_MISC_MMAP_BUILD_ID (1 << 14)
/*
* Reserve the last bit to indicate some extended misc field
*/
Expand Down Expand Up @@ -915,10 +937,20 @@ enum perf_event_type {
* u64 addr;
* u64 len;
* u64 pgoff;
* u32 maj;
* u32 min;
* u64 ino;
* u64 ino_generation;
* union {
* struct {
* u32 maj;
* u32 min;
* u64 ino;
* u64 ino_generation;
* };
* struct {
* u8 build_id_size;
* u8 __reserved_1;
* u16 __reserved_2;
* u8 build_id[20];
* };
* };
* u32 prot, flags;
* char filename[];
* struct sample_id sample_id;
Expand Down
32 changes: 28 additions & 4 deletions kernel/events/core.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -53,6 +53,7 @@
#include <linux/min_heap.h>
#include <linux/highmem.h>
#include <linux/pgtable.h>
#include <linux/buildid.h>

#include "internal.h"

Expand Down Expand Up @@ -397,6 +398,7 @@ static atomic_t nr_ksymbol_events __read_mostly;
static atomic_t nr_bpf_events __read_mostly;
static atomic_t nr_cgroup_events __read_mostly;
static atomic_t nr_text_poke_events __read_mostly;
static atomic_t nr_build_id_events __read_mostly;

static LIST_HEAD(pmus);
static DEFINE_MUTEX(pmus_lock);
Expand Down Expand Up @@ -4673,6 +4675,8 @@ static void unaccount_event(struct perf_event *event)
dec = true;
if (event->attr.mmap || event->attr.mmap_data)
atomic_dec(&nr_mmap_events);
if (event->attr.build_id)
atomic_dec(&nr_build_id_events);
if (event->attr.comm)
atomic_dec(&nr_comm_events);
if (event->attr.namespaces)
Expand Down Expand Up @@ -8046,6 +8050,8 @@ struct perf_mmap_event {
u64 ino;
u64 ino_generation;
u32 prot, flags;
u8 build_id[BUILD_ID_SIZE_MAX];
u32 build_id_size;

struct {
struct perf_event_header header;
Expand Down Expand Up @@ -8077,6 +8083,7 @@ static void perf_event_mmap_output(struct perf_event *event,
struct perf_sample_data sample;
int size = mmap_event->event_id.header.size;
u32 type = mmap_event->event_id.header.type;
bool use_build_id;
int ret;

if (!perf_event_mmap_match(event, data))
Expand All @@ -8101,13 +8108,25 @@ static void perf_event_mmap_output(struct perf_event *event,
mmap_event->event_id.pid = perf_event_pid(event, current);
mmap_event->event_id.tid = perf_event_tid(event, current);

use_build_id = event->attr.build_id && mmap_event->build_id_size;

if (event->attr.mmap2 && use_build_id)
mmap_event->event_id.header.misc |= PERF_RECORD_MISC_MMAP_BUILD_ID;

perf_output_put(&handle, mmap_event->event_id);

if (event->attr.mmap2) {
perf_output_put(&handle, mmap_event->maj);
perf_output_put(&handle, mmap_event->min);
perf_output_put(&handle, mmap_event->ino);
perf_output_put(&handle, mmap_event->ino_generation);
if (use_build_id) {
u8 size[4] = { (u8) mmap_event->build_id_size, 0, 0, 0 };

__output_copy(&handle, size, 4);
__output_copy(&handle, mmap_event->build_id, BUILD_ID_SIZE_MAX);
} else {
perf_output_put(&handle, mmap_event->maj);
perf_output_put(&handle, mmap_event->min);
perf_output_put(&handle, mmap_event->ino);
perf_output_put(&handle, mmap_event->ino_generation);
}
perf_output_put(&handle, mmap_event->prot);
perf_output_put(&handle, mmap_event->flags);
}
Expand Down Expand Up @@ -8236,6 +8255,9 @@ static void perf_event_mmap_event(struct perf_mmap_event *mmap_event)

mmap_event->event_id.header.size = sizeof(mmap_event->event_id) + size;

if (atomic_read(&nr_build_id_events))
build_id_parse(vma, mmap_event->build_id, &mmap_event->build_id_size);

perf_iterate_sb(perf_event_mmap_output,
mmap_event,
NULL);
Expand Down Expand Up @@ -11172,6 +11194,8 @@ static void account_event(struct perf_event *event)
inc = true;
if (event->attr.mmap || event->attr.mmap_data)
atomic_inc(&nr_mmap_events);
if (event->attr.build_id)
atomic_inc(&nr_build_id_events);
if (event->attr.comm)
atomic_inc(&nr_comm_events);
if (event->attr.namespaces)
Expand Down

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